The present invention relates to a tubular component used for drilling and operating hydrocarbon wells and landing heavy loads in a well or on or below the sea bed. The term “drill string or landing string component” means any element with a substantially tubular shape intended to be connected to another element of the same type or not in order, when complete, to constitute either a string for drilling or performing operations within a hydrocarbon well or a string for landing heavy loads in a well or on or below the sea bed. The invention is of particular application to other components used in a drill string or landing string such as drill pipes, heavy weight drill pipes, drill collars, and the parts of drill pipes, heavy weight drill pipes, and landing pipes which allow connection, and known as tool joints.
When a drill string is taken apart, removed, or connected, gripping slips are used to grip an area on the drill string or landing string component below the component being removed from, or connected to, the drill string or landing string.
Gripping slips have inserts with teeth to clamp the drill string or landing string component below the drill string or landing string component being removed or reconnected, and hold up the unsupported weight of the string below the slips. Due to repeated gripping of certain drill string or landing string components by the gripping slips, the area of the drill string or landing string component where gripping takes place may be more subject to fatigue failure from repetitive loading and unloading, and notching from each application of the slips' teeth. Accordingly, manufacturing a drill string or landing string component with a suitably long part life is challenging, since the components in a drill string or landing string must be capable in many cases of withstanding high tensile and compressive loads, bending and rotation under stress, as well as frequent slips clamping which results in hoop stresses, notching, and potential crushing of the drill string or landing string component.
U.S. Pat. No. 3,080,179 that issued Mar. 5, 1963 to C. F. Huntsinger claims a drill pipe construction with a thick-walled protector tube in the slip area of the drill pipe.
U.S. Pat. No. RE 37,167 re-issued May 8, 2001, to G. E. Wilson also claims an increased wall thickness steel protector tube for drill pipes, thus improving resistance to crack initiation and propagation.
Specifically Wilson proposed:
                “a thick wall rotary slip engaging elongated steel protector tube extending from the first tool joint to the main portion of the drill pipe, the protector tube having greater wall thickness than the main portion of the drill pipe, the protector tube being made of a Martensite steel having a small, close knit, grain size to reduce the penetration of the slip teeth that engage the protector tube when the joint is supported in the rotary table by slips”        
Wilson obtains a drill pipe with the protector tube that will run its full expected fatigue life without failing in notches and marks caused by slips in the rotary table.
Accordingly, increasing tube wall thickness where slips are applied on a landing pipe increases the landing pipe's resistance to stresses applied by the slips while the landing pipe is in tension. A trade-off between resistance to stresses and weight is needed to select tube wall thickness in the region where slips are to be applied.
Use of a material with a high Rockwell Hardness (HRC) makes the material stronger and the pipe more resistant to slip crushing, but more brittle and less resistant to crack initiation, and crack propagation, which may result from applying slips. In practice, yield strength ranges can be selected and the pipe treated accordingly to meet the desired material characteristics.